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## Stoichiometry

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**Stoichiometry**What’s that you said?**What is Stoichiometry?**• Stoichiometry is the numerical relationships in chemical reactions.**Let’s build a Tricycle(aka FSW3HP2)**• For each tricycle we need : • 1 frame (F) • 1 seat (S) • 3 wheels (W) • 1 handlebar (H) • 2 pedals (P) • The “chemical equation” for building a tricycle would look like: F + S + 3W + H + 2P → FSW3HP2**Tiny Tyke Workshop**• The Tiny Tyke workshop is scheduled to make 640 tricycles. How many wheels should be in the workshop to make these tricycles? • Analyze the knowns and unknowns: • Known: • The # of tricycles we need to build = 640 tricycles • Bal eq: F + S + 3W + H + 2P → FSW3HP2 • This balanced equation represents the formation of a single tricycle (FSW3HP2) • Therefore TT needs to make 640 FSW3HP2**Unknown:**• number of wheels = ? Wheels 3 W 1 FSW3HP2**We now solve for the unknown:**640 FSW3HP2 3 W = 1920 W 1 FSW3HP2 So you need 1920 wheels to make 640 tricycles. • Does this make sense??**Tiny Tyke has decided to make 288 tricycles each day. How**many seats, wheels and pedals are needed? • Do this as 3 separate problems: • Set up your ratios first: 1 S 3 W 2P 1 T 1 T 1 T • Now plug in what you’re given: 288 trikes 1 seat = 288 seats 1T**288 trikes 3 W = 864 wheels**1 T 288 trikes 2 P = 576 pedals 1 T**Stoichiometry**• Based on chemical equations and the law of conservation of matter • Must know the balanced chemical equation for the reaction we are studying first • You can determine the quantities of reactants and products in a chemical reaction from reaction stoichiometry**There are 4 types of reaction stoichiometry problems:**• mole-mole problems: • moles of A → moles of B • mole-mass problems: • moles of A → moles of B → mass of B • mass –mole problems: • mass of A → moles of A → moles of B • mass-mass problems: • mass of A → moles of A → moles of B → mass of B • What step do they all have in common?**Mole ratio**• The relationship between the number of moles of reactants and/or products in a chemical equation. • N2 (g) + 3 H2 (g) → 2NH3 (g) • The mole ratio of H to N is 3 : 1 • So… for every 1 mole of nitrogen, I need 3 moles of hydrogen • (and will produce 2 moles of ammonia)**Now lets Pracitce**• In the Synthesis of water, if I start out with 42 grams of H2 and an excess of 02, how much water will I have at the conclusion of the reaction?**Write the equation**H2 + O2 H2O • Balance the equation 2H2 + O2 2H2O • Start with what you know • 42 g H2**Now its**your Turn!**Butane (C4H10) undergoes combustion.**• Balanced Equation: • __ C4 H10 + __ O2 __ CO2 + __ H2O • How many grams of CO2 are produced when 88 g of O2 are reacted with an excess of butane?